Cooking ovens utilized for mass cooking of food products are well known in the art. For this process, a continuous oven having a heated gaseous cooking medium comprising a mixture of steam and air is made to flow over the food product while the food product moves through the oven by means of a conveyor. The temperature of the gaseous cooking medium may be between approximately 250.degree. F. and up to approximately 700.degree. for full or partial cooking. It is of course desired to make the cooking process as rapid as possible while obtaining the desired degree of cooking, browning and moisture content in the food product being cooked.
One cooking oven, as disclosed in U.S. Pat. No. 4,563,945, discloses a "controlled atmosphere oven" which allows adjustability of temperature and the proportion of steam in the gaseous cooking medium to provide the desired cooking atmosphere for the particular food product and the degree of doneness desired by the food processor. In this cooking oven, the gaseous cooking medium being a mixture of air and steam is heated to a high temperature and thereafter forced through a cooking chamber for cooking of a food product in the chamber.
The gaseous cooking medium is subsequently recirculated for reheating and circulation back into cooking chamber. The cooking oven comprises a movable hood which forms the upper portion of the enclosed cooking chamber of the oven. The hood portion can be raised from the base portion of the oven for cleaning interior surfaces of the oven quickly and efficiently so as not to inhibit rapid cooking of mass quantities of various food products. In this oven, the gaseous cooking medium is directed into the cooking chamber at a central location such that the gaseous cooking medium is made to flow over the food product in a direction opposed to the direction of conveyance or counterflow in a portion of the chamber. The counterflow helps reduce the cooking time as desired and also yields an efficient circulation configuration.
It should be recognized that the continuous flow oven shown in this patent enables the rapid cooking of mass quantities of food product but also requires high temperatures and atmospheric control or alternatively longer cooking times to obtain the desired browning of the outer surface of the food product as well as the degree of doneness or moistness sought by the food processor. In some situations, the continuous flow oven is not capable of optimally cooking the food product with the characteristics desired by the food processor. For example, by directing the heated cooking medium into the cooking chamber at a central location from which the cooking medium flows toward the ends of the oven, the portion of the conveyor system near the central location will necessarily receive higher temperatures than that portion near the ends of the oven as the cooking medium cools. In this construction of an oven, there may exist a temperature differential across the length of the conveyor of up to 80.degree. F.
Another problem associated with the continuous flow oven as disclosed lies in that the hood member subjected to the stress of thermal expansion during use of the oven which must be compensated for while maintaining separability of the hood member in relation to the bottom portion of the oven. The offsetting characteristics of strength and flexibility to allow thermal expansion of the hood member may result in the loss of thermal expansion capabilities on behalf of strengthening the hood member so as to not collapse under its own weight.
Another oven known in the prior art is shown in U.S. Pat. No. 4,834,063 which discloses an oven utilizing the impingement of a heated gaseous cooking medium on to the food product to more quickly and efficiently obtain the desired browning and/or crisping of the surface of the food product as well as achieve faster cooking times. In this type of oven, the temperature differential problem associated with the continuous flow oven previously described is alleviated as the air flow is across the conveyor belt rather than parallel to it. This oven also continuously circulates the gaseous cooking medium and allows the addition of moisture thereto for obtaining the desired characteristics of doneness and moistness. The cooking oven comprises impingement duct fingers for directing jet streams of the moisturized cooking medium onto a food product being conveyed through the oven. The gaseous cooking medium is heated and directed at a relatively high velocity to the duct fingers for impingement on the food product and is subsequently recirculated for repeating this cycle.
It should be recognized that as the distance between the duct fingers and food product increases, the heat transfer characteristics of the jet stream will be decreased necessitating longer dwell time in the oven for proper cooking of the food product. Similarly, the browning of the food product cannot be effectively and optimally achieved as the distance between the duct finger and food product increases. Although the structure of the cooking oven as shown in this application allows adjustment of upper duct fingers for optimum cooking of a particular food product, such adjustment cannot be made during operation of the oven, and the flexibility of using the oven to cook various food products in one cooking cycle is inhibited. Further, adjustment of the duct fingers is somewhat inconvenient and time consuming thereby limiting the use of such a feature in mass preparation of various food products. Other ovens utilizing impingement of a heated cooking medium may be found for example in U.S. Pat. No. 4,462,383.
It is also found in this type of oven that cleaning of all interior surfaces is somewhat inhibited due to the necessity of providing a supporting structure for the duct fingers which are disposed above the food product within the oven. The structure as disclosed in the above application comprises a plurality of access doors to the interior of the oven for maintenance and cleaning thereof. Although the access doors are provided for gaining entrance to the oven's interior, not all surfaces which need to be cleaned are accessible. To facilitate further cleaning of the oven, a mixture of steam and heated water is fed into the oven via the cooking medium moisturizing system for cleaning of surfaces in the vicinity thereof. Also, drippings from the food product or the like are continuously drained outwardly of the oven to reduce the necessary cleaning of the ovens interior. The cleaning procedures in combination allow for adequate cleaning of the oven but are somewhat time consuming and add costs to the oven.
Another problem associated with this type of oven is found in that any access doors must necessarily be sealed to prevent the egress of the gaseous cooking medium from within the oven. The sealing structure has presented a significant problem and results in additional costs in the manufacture of the oven.
It is also noted that the oven as shown in this application positions the heating and blowing means for circulation of the gaseous cooking medium at the top of the oven to enable circulation to the lower duct fingers of the apparatus. In this way, the height of the oven may present a problem to the food processor.